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Re: ?Secondary coil questions?



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Jay,

The resonant frequency calculation for the secondary coil is 1 / (2 x PI x SQRT(L x C)). The secondary's winding has an inductance (L) and a capacitance (C). The inductance is based on wire size, geometry, and current distribution. The capacitance is due to the capacitance between each turn. Those are the "basics". However, not all is included in this simple equation. Tesla Coils are air core transformers. The secondary is easily influenced by external capacitances and by the distribution of currents along the coils length which becomes less uniform at high frequency and in the presence of external capacitances. The main external influences are ground, objects near the coil, the primary, toploads, and the surroundings where the coil is measured or run. Their size and shape affect the self resonant frequency of the coil because both L and C will vary with their influence.

So, we use programs (as Terry explained) to figure out as many "influences" into the calculations as is humanly possible. The programs include many years of work, but that is usually not realized. It helps to understand just what the programs are doing and often it's good to measure and test measurements against program predictions. Terry, Carlos, Paul, and my own Javatc programs are very good at figuring out the L's and C's. There are some slight differences in our methods, but our results are extremely close.

Only a few years ago, the toploads influence was completely empirical and calculations simply used a percentage of influence to predict frequencies. Nowadays, we are actually computing the size, shape, and positional influence on the coil. This also includes the primary's external capacitance on the secondary. These are things best left to programs. Measuring is always an excellent cross check and I recommend that everyone measure as much as possible. Just keep in mind that when C and L is measured, such as a simple LCR meter, the measurements are for L's and C's where currents are uniform along the coil. It can be difficult to measure these things at resonant frequencies when the currents are not uniform. Thus, it takes specific equipment and methods, so good programs written specifically for Tesla resonators are very helpful.

All these programs are a direct result of Chip's TCML over these many years.

There is a document that Terry wrote which is very helpful for coilers regarding calculations. It's at his site and also at my own.

<http://www.classictesla.com/FormulasForTeslaCoils.pdf>http://www.classictesla.com/FormulasForTeslaCoils.pdf

Some of the programs at my site are:

<http://www.classictesla.com/java/javatc.html>http://www.classictesla.com/java/javatc.html (JAVATC - A Tesla Coil Design program)

<http://www.classictesla.com/fantc/fantc.html>http://www.classictesla.com/fantc/fantc.html (FANTC - A program to solve C's and L's).

<http://www.classictesla.com/java/javammc/javammc.html>http://www.classictesla.com/java/javammc/javammc.html (JAVAMMC - MMC Design Program)

<http://www.classictesla.com/java/2layer/duallayer.html>http://www.classictesla.com/java/2layer/duallayer.html (Dual-Layer Primary Inductance program)

<http://www.classictesla.com/java/platecap/platecap.html>http://www.classictesla.com/java/platecap/platecap.html (Plate Capacitor Design program)

<http://www.classictesla.com/java/rollcap/rollcap.html>http://www.classictesla.com/java/rollcap/rollcap.html (Rolled Capacitor Design program)

<http://www.classictesla.com/java/bottlecap/bottlecap.html>http://www.classictesla.com/java/bottlecap/bottlecap.html (Jar or Bottle Capacitor Design program)

Antonio Carlos M. de Queiroz has a bunch of excellent programs at:
<http://www.coe.ufrj.br/%7Eacmq/programs/>http://www.coe.ufrj.br/~acmq/programs/

Terry Fritz also has programs at:
<http://hot-streamer.com/TeslaCoils/Programs/Programs.htm>http://hot-streamer.com/TeslaCoils/Programs/Programs.htm

Paul Nichoson's TSSP site is filled with a great deal of up to date theory and TSSP software:
<http://www.abelian.demon.co.uk/tssp/>http://www.abelian.demon.co.uk/tssp/

Mark Rzeszotarski has an excellent Matual Inductance and Coupling program (MandK):
<http://hot-streamer.com/TeslaCoils/Programs/MANDKV31.ZIP>http://hot-streamer.com/TeslaCoils/Programs/MANDKV31.ZIP
http://hot-streamer.com/TeslaCoils/Programs/MANDKV31.PDF

More than you probably wanted with a simple question, but now and then it's good to point out some of these programs for the entire list. Many new coilers may not be aware of all the programs available.

Take care,
Bart

Tesla list wrote:
Original poster: <mailto:jhowson4@xxxxxxxxxxx>jhowson4@xxxxxxxxxxx

Question

How do you calculate the resonance frequency of the secondary coil with or with out a top load?

Jay Howson

<mailto:jhowson4@xxxxxxxxxxx>jhowson4@xxxxxxxxxxx